If you want a role-play reason to join the College, just walk up to the bridge and use the "Pff. [censored], please. I'm the Dragonborn." option. She'll say something along the line of "Oh, Dragonborn? Well, even though you aren't a Mage - we can still learn a great deal from each other. Please, follow me."

Though, you can eventually become the Arch-Mage, with no knowledge of any Magic beyond the Flames spell you're given at the start of the game. You can use shouts to get through everything in the quest line.

..So you might need to invent another role-playing reason for that, as well. =P

Guys guys. People always seem to forget something :X

http://www.uesp.net/wiki/Skyrim:Atronach_Forge

Atronach Forge ftw.
Turn that ebony bow into a deadric one and without having to get 90 smithing

Heads up though the ingredients required are rather hard to find.
Ebony Bow (unenchanted), Daedra Heart, Centurion Dynamo Core, Black Soul Gem.

The BIGGEST problem though is that it requires having a Sigil Stone in inventory and the Sigil Stone can only be obtained through the Conjuration ritual spell quest which requires having 90 conjuration before even being allowed to start the quest. Personally though even on my warrior toons i like having conjuration :X

Well, that's.....huh. Who'd a thunk it.

I'm level 38, and have deliberately avoided going anywhere but Whiterun, Riften and Markarth (I became overloaded with quests, and don't want any more right now). I've managed to find all those ingredients (I have no idea where), but don't have the 90 conjuration or Sigil.

Poop.